Structural Colors of Cyclic Diblock Copolymers Enabled by Topology-Driven Structural Ordering and Tuned by Blending with Constituent Cyclic Polymers

Controlling structural colors of high-molecular-weight (HMW) block copolymers is challenging due to their pronounced chain entanglements, often limiting accessible polymeric architectures required for self-assembly into photonic crystals. Here, we demonstrate tunable structural colors in photonic films induced by the self-assembly of simple cyclic diblock copolymers (CDCs). Thanks to the unique compounded sequence and spatiotemporal topology controls of Lewis pair polymerization, one-pot copolymerization of (meth)acrylic monomer mixtures furnishes the precision synthesis of well-defined CDCs with a HMW (862.4 kDa) at scale (20 g). The resulting CDC spontaneously self-assembles into a well-ordered lamellar structure, producing a vivid blue structural color. In situ small-angle X-ray scattering measurements reveal that the self-assembly of the HMW CDC occurs at a much faster rate than that of its linear counterpart, leading to long-range ordering with improved lamellar domain purity and avoiding a kinetically trapped morphology. Blending the CDC with the linear counterpart disrupts this coloration, coinciding with a loss of lamellar structural ordering. Owing to the cyclic topology-driven structural ordering, blending the CDC with cyclic polymer additives swells the lamellae up to 123% of the initial spacing, allowing for controlling the reflected wavelength spanning from 467 to 608 nm and accordingly producing blue to orange colors.